He'll serve the final three years of a four-year term started by Republican Merle Flowers of Southaven, who resigned to spend more time with family.
Parker jokingly told his colleagues to be patient as he learns their names.
The Senate usually has 52 members. There are two vacancies now because of the recent deaths of Democratic Sens. Bennie Turner of West Point and Alice Harden of Jackson.
Copyright 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.